An all-solid-state continuous-wave single-frequency laser is widely used in scientific research fields such as quantum optics, quantum information, cold atomic physics, and optical frequency standards because of its advantages of low intensity noise, high beam quality, high output power, high stability, and the like. In experimental applications such as cold atomic physics and optical frequency standards, to accurately match the output frequency of the laser with the atomic transition absorption line, a laser is required to have a certain capability of continuous frequency-tuning while having a relatively wide tuning range. To achieve output frequency tuning of the laser, one of the most common methods is to insert an etalon into a resonant cavity of a laser.
The frequency-tuning of an all-solid-state single-frequency laser can be achieved by adjusting the effective optical path of an etalon, for example, adjusting the incident angle of an etalon, adjusting the temperature of an etalon, or adjusting the refractive index of an electro-optic etalon using the electro-optic effect of an electro-optic crystal. After the etalon transmission peak is locked together with the oscillating mode of the laser resonant cavity in real time, continuous frequency-tuning of the all-solid-state single-frequency laser can be achieved by scanning the cavity length of the laser resonant cavity. However, an all-solid-state single-frequency tunable laser obtained by this method has a tuning range limited to a free spectral region of the adopted etalon. To obtain a wider tuning range, such as covering an overall gain line width of a laser gain medium, it is required to use a thinner etalon, usually of a few hundred micrometers, and meanwhile in order to ensure the mode selection capability of the etalon, it is required that the etalon is coated with a film having a certain reflectivity, or a combination of two etalons with different thicknesses is adopted, which on one hand increases the difficulty in designing and processing the etalon, and on the other hand increases the difficulty in designing the all-solid-state continuous-wave single-frequency laser.
Accordingly, it would be desirable to improve upon the conventional methods used for expanding a tuning range of an all-solid-state continuous-wave single-frequency laser.